The present invention relates to personal mobile computing devices commonly known as handheld portable computers. More particularly, the present invention relates to a system and method for enhancing speech recognition in mobile computing devices.
Mobile devices are small electronic computing devices sometimes referred to as personal digital assistants (PDAs). Many of such mobile devices are handheld devices, or palm-size devices, which comfortably fit within the hand. One commercially available mobile device is sold under the trade name HandHeld PC (or H/PC) having software provided by Microsoft Corporation of Redmond, Wash.
Generally, the mobile device includes a processor, random access memory (RAM), and an input device such as a keyboard and a display, wherein the keyboard can be integrated with the display, such as a touch sensitive display. A communication interface is optionally provided and is commonly used to communicate with a desktop computer. A replaceable or rechargeable battery powers the mobile device. Optionally, the mobile device can receive power from an external power source that overrides or recharges the built-in battery, such as a suitable AC or DC adapter, or a powered docking cradle.
In one common application, the mobile device is used in conjunction with the desktop computer. For example, the user of the mobile device may also have access to, and use, a desktop computer at work or at home. The user typically runs the same types of applications on both the desktop computer and on the mobile device. Thus, it is quite advantageous for the mobile device to be designed to be coupled to the desktop computer to exchange information with, and share information with, the mobile device.
As the mobile computing device market continues to grow, new developments can be expected. For example, mobile devices can be integrated with cellular or digital wireless communication technology to provide a mobile computing device which also functions as a mobile telephone. Thus, cellular or digital wireless communication technology can provide the communication link between the mobile device and the desktop (or other) computer. Further, speech recognition can be used to record data or to control functions of one or both of the mobile computing device and the desktop computer, with the user speaking into a microphone on the mobile device and with signals being transmitted to the desktop computer based upon the speech detected by the microphone.
Several problems arise when attempting to perform speech recognition, at the desktop computer, of words spoken into a remote microphone such as a microphone positioned on a mobile device. First, the signal-to-noise ratio of the speech signals provided by the microphone drops as the distance between the microphone and the user""s mouth increases. With a typical mobile device being held in a user""s palm up to a foot from the user""s mouth, the resulting signal-to-noise ratio drop may be a significant speech recognition obstacle. Also, internal noise within the mobile device lowers the signal-to-noise ratio of the speech signals due to the close proximity of the internal noise to the microphone which is typically positioned on a housing of the mobile device. Second, due to bandwidth limitations of digital and other wireless communication networks, the speech signals received at the desktop computer will be of lower quality, as compared to speech signals from a desktop microphone. Thus, with different desktop and telephony bandwidths, speech recognition results will vary when using a mobile computing device microphone instead of a desktop microphone.
A mobile computing apparatus, adapted to be held in the palm of a user""s hand, includes an antenna for transmission of information from the mobile computing apparatus. A first microphone, adapted to convert audible speech from the user into speech signals, is positioned at a distal end of the antenna. The antenna is rotatable, while the mobile computing apparatus is held by the user, into a position which directs the first microphone toward the mouth of the user.
In some embodiments of the invention, the antenna is rotatable to a position that, for a particular viewing angle and separation distance of the mobile apparatus relative to the user, minimizes the distance between the first microphone and the mouth of the user. Minimizing this distance increases the signal to noise ratio of the speech signals provided by the first microphone. The mobile computing apparatus can also include a second microphone, positioned on a housing of the apparatus or elsewhere, which together with the first microphone forms at least a portion of a three dimensional microphone array. The three dimensional microphone array also increases the signal to noise ratio.
The mobile computing device can be a cellular or digital wireless telephone. The mobile computing device can also be adapted to implement speech recognition processing of the speech signals.